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<concept id="GUID-2632A013-AA87-485E-855D-C50E211057D6" xml:lang="en"><title>Tactile

feedback implementation example</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>This is an implementation example of a simple tactile feedback enabled

control. This example can help give you an overall understanding

of what methods to implement and what are the typical actions in each function. </p>

<p>The example control uses area registry for producing basic feedback on

pointer down events, and instant feedback for producing sensitive feedback

on drag events when the control’s state changes.</p>

<p>The header file of the example control is presented below. </p>

<codeblock xml:space="preserve">#include &lt;coecntrl.h&gt;

class CMyTactileEnabledControl: public CCoeControl

    {

public:

    CMyTactileEnabledControl();

    virtual ~CMyTactileEnabledControl();

public: // from CCoeControl

    void HandlePointerEventL( const TPointerEvent& aPointerEvent );

    void SizeChanged();

    void PositionChanged();

    };</codeblock>

<p>Note that you do not necessarily need to implement any new functions for

supporting tactile feedback. But for non-window-owning controls that use area

registry, you have to override <codeph>PositionChanged</codeph>, because otherwise

you may end up with a situation where the control has been moved, but the

feedback area still remains in its original place.</p>

<p>The first part of the source file is presented below.</p>

<codeblock xml:space="preserve">#include &lt;touchfeedback.h&gt;

#include "mytactileenabledcontrol.h"

CMyTactileEnabledControl::CMyTactileEnabledControl()

    {

    // No Tactile Feedback related actions needed 

    // when the control is created.

    }

CMyTactileEnabledControl::~CMyTactileEnabledControl()

    {

    // Before destroying the control, you need to call 

    // RemoveFeedbackForControl, first, for removing all remaining

    // feedback areas, and, second, for clearing this control's   

    // state information stored by the Tactile Feedback Client API.

    MTouchFeedback* feedback = MTouchFeedback::Instance();

    if ( feedback )

        {

        feedback->RemoveFeedbackForControl( this );

        } 

    }

</codeblock>

<p>The code above illustrates that usually nothing needs to be done (from

the tactile feedback point of view) when a control is constructed, but you

must always call <codeph>RemoveFeedbackForControl</codeph> at the destructor

if you have added any feedback areas with the <codeph>SetFeedbackArea</codeph> function,

or disabled or enabled feedback with the <codeph>EnableFeedbackForControl</codeph> function.</p>

<p>Also notice that you must use <codeph>MTouchFeedback::Instance</codeph> in

the destructor (and not any stored pointer), because in some rare cases the

feedback system may already have been destroyed before the last controls are

deleted.</p>

<p>The remaining part of the source file is displayed below.</p>

<codeblock xml:space="preserve">void CMyTactileEnabledControl::HandlePointerEventL(

    const TPointerEvent& aPointerEvent )

    {

    TBool stateChanged;

    // (your code here)

    if(aPointerEvent.iType == TPointerEvent::EDrag && stateChanged)

        {

        // Producing sensitive feedback when dragging causes a state

        // change (this kind of feedback triggering is not possible  

        // by using area registry).

        MTouchFeedback* feedback = MTouchFeedback::Instance();

        if ( feedback )

            {

            feedback->InstantFeedback( ETouchFeedbackSensitive );

            }

        }

    }

void CMyTactileEnabledControl::SizeChanged()

    {

    // (your code here)

    // We have to update all feedback areas when control is resized.

    // This is also enough for adding the feedback area in the first

    // place, because SizeChanged is always called after control has

    // been created and positioned on screen.

    MTouchFeedback* feedback = MTouchFeedback::Instance();

    if ( feedback )

        {

        feedback->SetFeedbackArea( 

            this,

            0, // Area index, use 0 when only one area in this control

            Rect(), 

            ETouchFeedbackBasic,

            ETouchEventStylusDown );

        }    

    }

void CMyTactileEnabledControl::PositionChanged()

    {

    // We have to update our feedback area when this control 

    // is moved. One way to do this is to call SizeChanged here.

    SizeChanged();    

    }

</codeblock>

<p>You are recommended to put feedback area updates into a new <codeph>UpdateFeedbackAreas</codeph> function,

and then to call this from both the <codeph>SizeChanged</codeph> and <codeph>PositionChanged</codeph> functions.</p>